Enclosed fuse



April 8, 1941. C HART 2,237,933

ENCLOSED FUSE Filed Oct. 31, 1938 234542 4 '45 45 55 3&1

INVENTOK 4557-51? CI Hm??- BY MWQZ M ATTORNEYS Patented Apr. 8, 1941 UNITED STATES PATENT OFFICE ENCLOSED FUSE Lester 0. Hart, Cleveland, Ohio, assignor to Hi- Voltage Equipment Company, Cleveland, Ohio, a corporation of Pennsylvania Application October 31, 1938, Serial No. 237,842

4 Claims.

- This invention relates to fuses for electrical circuits and more particularly to the type of fuse disclosed in my prior Patent 1,605,543, dated November 2, 1926, and constitutes an improvement thereon.

Under some conditions of operation, such as an overload of very short duration that drops to a low or normal current just at the instant the fuse melts, there is not suificient energy in the are that is established to develop the necessary explosive pressure within the fuse tube to expel the fuse link and, as a result, the arc is not extinguished and progresses along the tube and consumes the link and, in addition, seriously damages or destroys the fuse tube.

It is one of the objects of the present invention to insure successful operation of the fuse under all conditions ofload by the provision of additional mechanism for quickly removing the entire fuse link from the tube, regardless of the explosive pressure that is generated therein, when the calibrated fusible section of the link melts.

A further object of the invention is to combine with a fuse structure, such as that disclosed in my prior Patent 1,605,543, a fuse link that will be made up of several sections joined together in series by fusible sections or joints so that when the link is expelled from the tube it will be in disconnected sections which are of insufficient length to form a short-circuit across adscription taken in connection with the accom- I panying drawing, in which Fig. 1 is a side elevation of a fuse structure embodying my invention.

Fig. 2 is an end elevation thereof as viewed from the right of Fig. 1.

Fig. 3 is a plan view of the right hand terminal,

shown in Fig. 1, with the mechanism for withdrawing the fuse link shown in its normal or operative position.

Fig. 4 is a view similar to Fig. 3 but showing the mechanism for withdrawing the link in the position it assumes after it has operated to withdraw the link, and

Fig. 5 is an enlarged section of the end portion of my improved fuse link that is located in the closed end of the fuse tube and comprises the calibrated fusible section of the link.

Referring to the drawing, I0 is a base carrying the posts II and I2 upon which are mounted the insulators l3 and 14. The insulator l3 carries a metal bracket or yoke l5 having an arm IE to which an electrical conductor may be attached. The bracket l5 has a pair of upwardly projecting arms I! which are suitably spaced apart to receive between them the metal casing l8 of the fuse tube. This casing has a pair of laterally projecting lugs l9 that engage in suit-able slots in the arms ll. The bracket l5 also has a split collar 23 for securing the opposite end of the casing IS. The casing l8 has a plug 2| secured in one end thereof, and this plug has a lug 22 to which the terminal 23 of the fuse link is secured. The opposite end of the casing 18 is internally threaded to receive the tube 24, of insulating material.

The insulator l4 carries a bracket 25 having an arm 26 to which a conductor may be attached. The upper end of the bracket 25 is provided with the laterally projecting arms 21 and 28 which form a yoke in which the arm 29 is mounted, this arm being adapted to swing on the pivot pin 30. The arm 29, as will be seen from Fig. 2, comprises the 'members 3| and 32 which are separated by the spacers 33 and secured by rivets 34, or in any other suitable manner. The arm 29 carries the spaced rods 35 which normally engage with the tube 24, as shown in Figs. 1 to 3, the purpose of these rods being to bring the open end of the tube 24 to line potential, thus shielding the fuse link from corona discharge.

The bracket 25 has a laterally projecting post 36, preferably of conical form and positioned as shown in Figs. 3 and 4. The fuse link 31 has a loop 38 at one end and this loop is arranged on the post 36, the opposite end of the fuse link being secured to the lug 22, as previously described.

A torsion spring 39 is arranged on the pivot 33 with the end 40 in engagement with the bracket 25 and the end 4| in engagement with one of the spacers 33. When the arm 29 is in the position shown in Fig. 3 the spring 39 is under tension tending to swing the arm in the direction of the arrow. It will be noted that the spacer 33 at the outer end of the arm 29 engages with the fuse link 31 at a point outside the tube 24 but adjacent the end thereof.

I prefer to use a fuse link of the type described and claimed in my copending application Serial No. 237,843, filed October 31, 1938, and, in the drawing, I have illustrated a fuse link of this type which comprises, in addition to the calibrated fusible section 42, a series of conductor sections .43 which are connected together in end to end or series arrangement by fusible tubular sections or joints 44 which are calibrated to fuse after the fusible section 42.

The operation of the fuse mechanism is as follows: Assuming that it is set as shown in Figs. 1 to 3, it will be apparent that the fuse link 31 will be under constant tension due to the pressure of the arm 29 thereon. When an overload occurs the fusible section 42 of the fuse link will melt and the gases generated by the arc, thus formed, will create an explosive pressure which will usually blow the remaining portion of the fuse link out of the tube 24 and the loop 38 will be disengaged from the post 36 and thus the fuse link will be thrown entirely away from the fuse mechanism. The provision of the fusible sectionsor joints 44 in the link will result in the link being expelled from the tube 24 in relatively short pieces which will not have sufficient length to form a short circuit across any pair of conductors or to ground any conductor.

When the fusible section 42 of the link is melted the arm 29 is thereby released and the spring 3 9 will swing the armaway from the tube 24 and into the position shown in Fig. 4, this movement of the arm 29 serving to whip or cast the fuse link entirely away from the apparatus. Under some conditions a momentary overload might be sufiicient to melt the fusible section 42 without causing sufficient arc, to generate the gases required to expel the fuse link from the tube 24 and, as a result, if the arm 29 were not present in the apparatus, the arc would tend to burn slowly along the fuse link and thus destroy the tube 24. However, the presence of the arm 29 in the apparatus insures the withdrawal of the fuse link from the tube 24 regardless of the amount of gases that are generated by the arc that is formed.

Under some conditions of operation a momentary overload may weaken but not be of sufiicient duration to fuse or melt the fusible section 42. When this occurs it is desirable that the fusible section 42 shall not be ruptured by the tension produced by the arm 29 and, therefore, I prefer to use a reenforcing wire 45 between the terminals of the fusible section 42. This wire 45 is preferably of a fine gauge and of a material having a high tensile strength, such as stainless steel,'so that it will have a relatively low currentcarrying capacity in comparison with the capacity of the fusible section 42. With the reenforcing wire 45 present, as shown in Fig. 5, it will prevent the fusible section 42 from being ruptured by the tension in the fuse link or when there is a momentary overload that does not melt the fusible section 42 but merely weakens it. If the overload current is s'umcient to fuse the fusible section 42 of the link it will also fuse the reenforcing wire 45 and the apparatus will function in the normal way.

While I have illustrated and described what I now consider to be the preferred form of my invention, it will be understood that various changes may be made in the details of construction that have been illustrated and described without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, I claim:

1. In a fuse, the combination of a pair of terminal members, insulators for supporting said terminal members, a tube closed at one end and open at the other and having its closed end mounted onone of said terminal members, a fuse link extending through said tube and having a fusible section at the closed end of the tube electrically connected with the last mentioned terminal member, the other of said terminal members having a post thereon, said fuse link having a pendently supporting said terminal members, a

tube closed at one end and open at the other and having its closed end mounted on one of said terminal members, a fuse link extending through said tube and having a fusible section at the closed end of the tube electrically connected with the last mentioned terminal member, the other of said terminal members having a post thereon, said fuselink having a loop at the end thereof which is outside said tube, said loop being loosely mounted on said post, an arm pivotally mounted on said other terminal member and engaging said link only at a point adjacent the open end of said tube, and a spring for swinging said arm in the direction to subject said link to tension andto withdraw the link from said tube and throw said loop off said post upon the rupturing of said fusible section.

3. In a fuse, the combination of a pair of terminal members, spaced insulators for independently supporting said members, atube closed at one end and open at the other and having its closed end mounted on, one of said terminal members, the other of said members having a post thereon, a fuse link extending through said tube and having a fusible section at the closed end of the tube electrically connected with the last mentioned terminal, said link extending from the open end of said tube and being provided with a loop which is loosely mounted on said post, means engaging said link at a point outside of said tube for subjecting the link to tension. and whereby the link will be automatically withdrawn from the tube thrown off said post upon the rupturing of said fusible section, said link having a reenforcing wire of material of high tensile strength but low current-carrying capacity in comparison with said fusible section, spanning the space between the ends of said fusible section and adapted to prevent the tension to which the link is subjected from breaking said fusible sec.- tion when the latter is subjected toa momentary overload current which weakens the fusible section without actually fusing it.

4. In a fuse, the combination of a pair of terminal members, spaced insulators for independently supporting said members, a tube closed at one end and open at the other and havingits closed end mounted on one of said terminal mem bers, the other of said members having a. post thereon, a fuse link extending through said tube and, having a fusible section at the closed end. of the tube electrically connected with the last mentioned terminal, said link] extending from the open end of said tube and being provided with a loop which is loosely mounted on said post, said link comprising a plurality of conductor sections joined together in series by fusible sections which, when the first mentioned fusible section fuses, will be fused subsequent thereto, so that said link :vill be expelled from said, tube in detached secions.

LESTER C. HART; 

